This invention relates to chemical, petrochemical or oil refining process equipment in which liquid is contacted with gas or vapor. This liquid-gas contact may be used for mass transfer where a component from the gas or vapor is absorbed by the liquid or a component from the liquid is stripped by the gas or vapor. It also may be used for heat transfer between the liquid and the gas or vapor.
The invention is specifically related to trays with cross-flow in which the liquid passes from one tray to the tray below through downcomers, while the gas or vapor passes though the trays openings covered by the valves. The trays are arranged horizontally within a tower or column. The gas or vapor goes from the bottom to the top of the column, while the liquid flows on each tray horizontally (creating the “cross-flow” respect to the up-flow of the gas or vapor) from one side of the tray to the other where it enters the tray downcomer to go to the tray below. The horizontal liquid flow across the tray is what is described as the “liquid design flow direction”.
The valves that cover the openings on the trays allowing the gas or vapor to pass can be fixed or movable. The fixed valves do not move, while the movable valves respond to the pressure of the up-flowing gas or vapor. The present invention relates to both, fixed and movable valves.
The typical valve configuration ranges from round to trapezoidal as seen from above. Round valves have the disadvantage of allowing part of the gas or vapor to flow opposite to the liquid design flow direction, which creates restrictions to the liquid flow and in the downcomers (by those valve rows close to the downcomer from the tray above). These restrictions reduce the hydraulic capacity of the trays.
The configuration of a rectangular or trapezoidal valve creates less restriction to the liquid flow. However, the first leg of the valve, the leg upstream of the opening respect to the liquid design flow direction, still creates restriction to the liquid flow and promotes solid deposition in fouling systems which may limit the tray hydraulic capacity.
The present invention provides a simple design of a fixed or movable valve that minimizes restrictions to the liquid flow and avoids solid accumulation and deposition on the tray. This improves the tray performance in fouling systems and maximizes the hydraulic capacity of the trays.